With the rapid expansion of computer operations into all aspects of business and government, many hundreds of thousands of people are involved in the operation of computer video display terminals. Many operators are positioned at the terminals during most of their working day, focusing on characters on the screen at a fixed focal distance, and exposed to the light radiating from the fluorescing pigments in the CRT screen. Increasingly, video display terminal operations are being linked to job-related stress and visual impairments.
Medical concern about the contribution of video display terminal use to eye impairment and stress is increasing. Although medical investigators, including the 1983 National Research Counsel Report, have produced no definitive evidence that prolonged video display terminal exposure produces ocular pathology, operators do suffer from certain ocular symptoms. Individuals at the workstation, especially after a stint of several hours, may have headaches, ocular pain, blurring, diplopia, congestion and ephiphora--otherwise known as the "VDT Syndrome".
I have found that the complaints, other than those derived from uncorrected refractive errors and eye muscle problems, can be traced to glare, light reflections, accommodative spasm and mental stress. The cornea, iris, lens and retina are sensitive to ultraviolet light (UV). The cornea is particularly susceptible to UV damage. Corneal epithelium may slough off and result in keratitic inflammation. With more severe exposure, iritis can occur. The human crystalline lens may have an increase in chromophole cells, leading to discoloration, and in the extreme, cataract formation. UV light can cause retinal irritation and/or damage, such as macula cyst or holes. Accommodative spasm is an overactivity of accommodation wherein the refractive power of the eye is increased and the patient experiences temporary myopia. The observer becomes temporarily near-sighted as the result of ciliary muscle spasm. It may be a response to fatigue. These symptoms can be induced and/or exaggerated by mental stress.
Although numerous legal judgments have been obtained on the basis of eye damage from VDT use, medical opinions about the long term damage potential of VDT use are divided. In the report "Video Displays, Work, and Vision" by the Panel on Impact of Video Viewing on Vision of Workers, Committee on Vision, Commission on Behavioral and Social Sciences and Education, National Research Council published by the National Academy Press, Washington, D.C. (1983) finding that radiation damage or serious diseases such as cataracts are not caused by VDT use, DR. 1. STARK, Professor of Physiological Optics and Engineering Science of the University of California, Berkeley (Appendix C) noted that ocular discomfort and visual fatigue beyond that appropriate for a normal workplace is indisputably related to VDT use. Although the ultraviolet (UV) radiation level emitted from CRT screens is generally believed to be below the level causing UV radiation damage to the ocular system, further research to identify the consequences of the UV radiation was recommended by Lerman, S. et al, "Ultraviolet Radiation Protection." 11(1):39-45 (1985).
This invention relates to a cover panel or faceplate which increases eye comfort of the user by filtering certain objectionable frequencies from the spectrum of light emitted by the screens and providing an optical adjustment of the focal distance for screen viewing of the viewer.